The proposed research will expand the capabilities of the vascular oxygen mapping in tissue based on the phosphorescence imaging method for the animal research as well as develop modified dyes potentially capable of approval for clinical use of the technique. The prototype commercial instrument OXYMAP(TM) developed in Phase I will be mated to an epi-illuminating microscope for greater sensitivity as well as for greater spatial resolution, The latter will be accomplished by implementing optical sectioning and deconvolution based on multiple images centered on different levels in sampled layer. Hardware and software will be developed for a prototype three dimensional oxygen concentration imaging instrument. This development will improve the existing capability to distinguish between different oxygen concentrations the same image area. A physical model of three dimensional oxygen concentration will be used to test the instrument. Spatial resolution will be measured in vivo by imaging oxygen concentration in cerebral tissue. Chemical modifications will be made of existing oxygen probes such that they are excreted in the urine via the kidneys without being metabolized. This will minimize retention time in the body and any potential for toxicity, and make the probes potentially suitable for clinical use.